This invention broadly relates to an element for an external ring fixator used for stabilizing bone fractures in orthopedic surgery.
More particularly, the invention relates to a clamp element for external fixators of the rod and ring type used for stabilizing bone fractures in orthopedic surgery; such clamp element secures at least one of the bone fragment stretching wires and the bone screws to one of the fixator rings.
As it is known in this technical field, external fixators are modular apparatuses, comprising a plurality of component parts, which can be assembled with each other into a variety of different configurations.
A typical example of this kind of fixator apparatuses is the Ilizarov system, wherein bone fragment fixing rings can be assembled with each other by means of extendible connecting tie rods or plates.
Such fixator apparatuses allow complex bone fractures to be recomposed, e.g. in the case the bone end of a limb has been splintered and one or more bone fragments happen to be dislocated from said bone end.
In such cases, stretching wires are suitably used; such wires have an end threading a hole drilled in the bone fragment, and bent over it in order to hold it in place. The opposite end of the stretching wire is made fast to one of the rings and here held.
In the Ilizarov system, the means used for securing the end of the stretching wire to the rings consists of simple bolts, inserted in holes made in the rings, and their associated nuts. Alternatively, special bolts having a hole drilled crossly to their threaded shank may be used; the hole receives the end of the stretching wire which is then clamped on the ring by means of a nut.
In some cases, for example when the bone fragment to recompose occurs at an intermediate location of the limb, the end of the stretching wire must be fastened at an angle to the plane containing the ring. In such cases, articulated clamp elements are used, which usually comprise a first portion secured to the ring and a second portion inclined to the plane of the ring and having clamping means of the stretching wire end.
Furthermore, different conditions of the bone fracture can require that a bone screw be used having a threaded end engaged in the bone cortex, and having an opposite screw-handling to be end secured to one of the rings. Here again, a respective different clamp element must be provided.
Thus, a multiplicity of clamp elementsxe2x80x94differing from one another by their type, function and assembling methodxe2x80x94must be made available, depending on whether the stretching wire for bone fragments or a bone screw is to be secured to the ring. This obviously involves higher manufacturing cost, since large volume production methods cannot be applied.
In addition, the provision of a range of different clamp elements implies the disadvantage for the orthopedic surgeon, who has always the duty to select the most suitable element to complete the installation of the fixator device. This selection requirement works against the necessity to have the fixator apparatus assembling and setting operations completed within the shortest possible time.
The underlying technical problem of this invention is to contrive a clamp element, particularly to be used in external fixator apparatuses of the rod and ring type, with such structural and functional features as to allow its universal application in a variety of assembling situations and conditions, and accordingly, its manufacture in large volumes. The limitations and drawbacks of the solutions presently proposed in the prior art would thus be overcome.
The resolutive idea of this invention is to arrange for a clamp element to comprise a pair of portions articulated with each other by a pivotal connection, each of such portions being interchangeably usable to secure the clamp element either to one of the fixator apparatus rings, or to a bone fragment stretching wire, or to a bone screw.
Based on this resolutive idea, this invention provides a clamp element as previously indicated and defined in the characterizing portion of claim 1.